Traditionally, absorbent articles have included a central absorbent portion having a body facing side, a garment facing side, longitudinally extending sides and transverse ends. These articles generally include an absorbent core made of loosely associated hydrophilic materials, such as wood pulp, that is covered on the body facing side by a layer of body fluid pervious material and on the garment facing said by a layer of body fluid impervious material. These layers are sometimes sealed around the absorbent core by joining them together along the longitudinal sides of the article so as to form laterally extending flanges--see, for example U.S. Pat. No. 4,678,527 (Ulman). The layer forming the body facing side is sometimes formed from an apertured plastic film which gives the surface of the article a feeling of dryness against the skin.
Typically absorbent articles are held in place by pressure sensitive adhesive on the garment facing side which adheres to the inner crotch surface of the user's undergarment. The fit of such absorbent products may be improved by imparting an arcuate shape to the article in the longitudinal direction. This is typically accomplished by applying longitudinally extending elastic elements placed in tension to the article--see, for example U.S. Pat. No. 3,236,238 (Morse) and U.S. Pat. No. 4,432,823 (Moore).
One drawback of prior art absorbent articles in which the layers are joined by forming flanges, as previously discussed, is that although the flanges are flexible with respect to forces acting perpendicular to the plane of the flange, they are fairly rigid with respect to forces acting in-plane. Consequently, the flanges of such articles have a tendency to dig into the skin of the user, causing discomfort.
Another drawback arises if the aforementioned apertured plastic film is used. Typically, such film is used to cover the sides of the article which bear against the user's thighs, as well as the upward facing portion of the body facing surface that is subjected directly to the fluid flow. Experience has shown that although the apertured plastic film feels dry against the skin, when pressed against the user's thighs it produces the unpleasant hot and sticky feeling associated with plastics.
Typically, absorbent articles are subject to lateral leakage under certain circumstances--for example, if the article is locally not in contact with the perineum because of wrinkling or deformation of the article or if the flow exceeds the local absorbent capacity of the article. Such lateral leakage causes fluid to flow along the surface of the perineum to the user's legs resulting, at the least, in soiling of the undergarment. Accordingly, napkins having wings extending from the longitudinal sides have been developed to protect the undergarment crotch from soiling--for example, see U.S. Pat. No. 4,285,343 (McNair). Unfortunately, lateral leakage can result in flow down the user's legs that soils other articles of clothing not protected by the wings.
U.S. Pat. No. 4,589,876 (Van Tilburg) discloses a sanitary napkin having wings in which flexible axes are formed that allow the wings to be folded over the edges of the panty crotch. Each wing is joined to the central portion of the napkin along a preferential bending line. The width of the central portion is less than the span of the perineum so that the elastic in the panty crotch bends the wings upward around the preferential bending line. This bending action causes the wings to form walls that bear against the laterally outward surfaces of the perineum to produce a seal that is described as being gasket-like. Unfortunately, such articles suffer from several drawbacks.
First, since the article relies on the panty elastic to bend the wings upward around the laterally outward surfaces of the perineum at the preferential bending joints between the wings and the central portion, the maximum width of the central portion is limited to the width of the panty crotch. This limits the absorbent capacity of the napkin as well as its applicability to a large variety of user/panty sizes.
Second, since the wings are folded over the edges of the panty crotch, the seals formed thereby can extend beyond the edges of the crotch only by the thickness of the wings. As a result, optimal contact of the seal with the body will not be attained for all users since the seal does not extend a substantial distance beyond the edge of the crotch. Again, this limits the applicability of the napkin.
Third, although the preferential bending line and flexible axis give the wing flexibility in the direction normal to the plane of the wing, the wing is relatively stiff with respect to a compression force applied in the plane of the wing. Hence, the compliancy of the wings is low, resulting in discomfort due to the wings digging into the body.
Fourth, since the elastic portion of the crotch is disposed at the top of the wall formed by the wing, the force imposed by deformation of the elastic portion acts to press only the wing against the user's body. The elastic portion does not push the central portion of the article against the perineum so as to ensure proper contact.
U.S. Pat. No. 4,701,177 (Ellis et al.) discloses a napkin in which the absorbent core in the longitudinally middle portion of the napkin has a dog bone shape--that is, the thickness of the central portion is increased but its width is reduced--created by pinching in the sides of the absorbent core in the middle portion. The cover and barrier are joined along a joint line that follows the contour of the central absorbent. As a result, in the reduced width middle portion of the napkin, the portions of the cover and barrier outboard of the seal line form walls. Elastic members disposed within the walls cause them to extend upward above the body facing surface and into the crease at the sides of the pudendum so as to prevent leakage. However, this arrangement suffers from several drawbacks.
First, as a result of the placement of the joint lines at the top of the sides of the central portion, the walls have a tendency to fold inward about the joint lines in use so that they lay over the body facing surface, thereby reducing the effective area of the central absorbent portion. Second, creating the walls requires that the central portion be formed into a dog bone shape so that this sealing approach is not applicable to all types of napkins. Third, the materials that form the walls are limited to those suitable for napkin covers and barriers.
U.S. Pat. No. 4,695,278 (Lawson) discloses a diaper in which flaps are formed by extending the cover and barrier beyond the sides of the central portion and joining them together along longitudinally extending joint lines spaced transversely from the central portion sides. Elastic members are disposed within the flaps, forming members characterized as "gasketing cuffs." Members characterized as "barrier cuffs" are formed by attaching strips of material, folded over so as to form loops at their distal ends, to the flaps along the joint lines. Elastic members are disposed within the loops causing them to extend vertically upward above the body facing surface. Unfortunately, as a result of the length of the barrier cuffs and the spacing of the joint lines away from the sides of the central portion, in use the barrier cuffs, like the walls in the Ellis patent, have a tendency to fold inward about the joint lines so that they lay over the body facing surface, thereby reducing the effective area of the central absorbent portion.
Consequently, it would be desirable to provide an absorbent article that overcomes the aforementioned drawbacks associated with absorbent articles heretofore known in the art. Such an article should be capable of forming a gasket-like seal to prevent lateral leakage of fluid yet avoid reducing the effective area of the central absorbent and be adapted to fit properly regardless of the size of the user or the undergarment. In addition, although being adapted to press against the user's body, the gasket should have sufficient compliancy to provide a comfortable fit and the appropriate surface properties necessary to minimize the unpleasant sensation of such contact. It would also be desirable that such a gasket be advantageously adapted to winged articles so that the wings and the gaskets cooperated to ensure a good fit and proper contact of the gasket and the central portion with the body.